Liquid pumping apparatus



Feb. 28, 1961 T. B. PHILIP 2,972,960

LIQUID PUMPING APPARATUS Filed Sept. 5. 1957 FEGB United States Patent 2,972,960 noun) PUMPING APPARATUS Thomas Bruce Philip, Eifingham, England, assignor to The Distillers Company Limited, Edinburgh, Scotland, 'a British company The present invention relates to apparatus for pumping readily vapourisable liquids, such as for example, liquid carbon dioxide.

This application is a continuation-in-part application of my co-pending application Serial No. 464,720, filed on October 26, 1954 (now abandoned).

In pumping readily vapourisable liquids difliculty is often experienced in preventing the pump from becoming filled with vapour from the vapourised liquid. For instance, when pumping liquid carbon dioxide from a storage tank in which it is commonly stored at pressure of about 300 p.s.i. and temperatures of F.; unless there is a considerable static head the liquid carbon dioxide will vapourise in the pump suction line as the pressure is reduced and it is impossible to operate the pump. Similarly, when the pump is being used intermittently external parts of the pump tend to rise in temperature by heat conduction from the surrounding atmosphere and when the pump is set in motion after it has been at rest, it tends to become flooded with the vapour, and, as a result, fails to function.

A method has now been found of ensuring the satisfactory operation of pumps working with such liquids, and it is of particular value where the pump is required to work intermittently. In this method the pump body is connected to a surface condenser which is cooled to a temperature lower than that of the readily vapourishable liquid being pumped. Any vapour formed in the pump passes into the condenser wherein it is reconverted into liquid with the result that the pump is at all times filled with liquid and is in a state to pump liquid when the pump is set in motion.

Accordingly, the present invention is an apparatus for pumping readily vapourisable liquids comprising a pump having a pump casing enclosing at least one pumping chamber and at least one moveable member operable therein to exert pressure upon the liquid being pumped, a condenser consisting of a metal tube, one end of which is attached to the said pump casing and being in communication with the pumping chamber, the other end of which is closed at least for part of the pumping cycle, and a jacket for cooling medium around said tube whereby vapour in the pumping chamber passes into the condenser where it is condensed.

Any type of pump may be used in the apparatus of the present invention, for example a diaphragm pump or reciprocating pump. Where reciprocating pumps are used these may be single or double acting and having cylinders arranged side by side, radially or in any other desired way.

It is preferred, however, that the pump shall be a diaphragm pump since these are very suitable for pumping readily vapourisable liquids, particularly when variable deliveries of such liquids are likely to be required.

The condenser which is connected to the pump body,

may be of any type of surface condenser, that is a condenser in which the vapour to be condensed is separated from the cooling medium by a surface of metal or similar heat conducting material. Conveniently the condenser may consist of a metal tube closed at the upper end and surrounded by a jacket in which circulates the cooling medium from refrigerating equipment. If desired means may be provided for the intermittent release of carbon dioxide vapour from the condenser whereby further evaporation takes place in the condenser, thereby assisting in the cooling of the condenser. If desired more than one such condenser may be connected to the body of the pump. Condensers such as those described above may be positioned at the top of the pump body in such a way that any carbon dioxide vapour present in the pumping chamber is not trapped in this chamber but rises in to the condenser wherein it is condensed and returns to the pumping chamber. Such condensers are preferably positioned in the vicinity of the inlet duct and between the inlet and outlet valves.

It is preferred, however, in the apparatus of the present invention that the condenser shall consist of a metal tube fixed to the pump casing at one end and being in communication with the pump chamber at that end and at the other end being in communication with the inlet and outlet valves of the pump, for example being affixed at that end to, and being in communication with, a chamber containing the inlet and outlet valves of the pump in the walls of the chamber. Such valves may vary suitably be ball valves, which may loaded as desired.

There are considerable advantages derived from such a preferred arrangement. For example, the incoming liquid carbon dioxide is mixed with cooled liquid already present in the condenser and is thus rapidly cooled. Further more, since the inlet and the outlet valves are separated from the pumping chamber by the length of the condenser, the pump chamber is mainly filled with cooled liquid during the pumping since the incoming liquid to be pumped is drawn into the pump through the inlet valve and ejected through the outlet valve without fully mixing with the cooled liquid in the pumping chamber and in the lower half of the condenser. Since, by this means, the pumping chamber is filled, when pumping, with cooled liquid the possibility of vapour locks in the pump is decreased. This is particularly true when a diaphragm pump is used where less heat arises due to frictional contact in the pump. t

It has been found advantageous in order to obtain fully the advantages noted in the preceding paragraph, to make the internal volume of the passage between the pumping chamber and the valves greater than the maximum'displacement of the diaphragm or piston of the pump. By this means it is ensured that some-of the cooled liquid remains in the passage during pumping, thus. providing cooled liquid to mix with the incoming liquid to be pumped and to ensure that cooled liquid is present; in the pumping chamber.

The jacket for cooling medium around the preferred form of the condenser may surround a portion of the condenser only or it may, if desired, be large enough to surround the valves of the pump and/or the pump casing in addition to the condenser itself.

Where the jacket is large enough to surround the valves and/or the pump casing the cooling liquid surrounding the condenser may be cooled by a pipe or pipes through which refrigerant is circulated, rather than by circulating a larger body of cooling liquid through a refrigerant system.

Additionally the outer surface of the jacket may be insulated against heat loss.

In the accompanying diagrammatic drawing, Figure l v shows a single acting piston pump fitted with a closed be gravity operated or spring surface condenser, Figure 2 shows a double acting piston pump fitted with one condenser on either side of the piston, Figure 3 shows a condenser provided with a valve for the continuous or intermittent release of carbon diox ide, Figure 4 shows a vertical section through a diaphragm pump, condenser and valve chamber in which the condenser only is surrounded by cooling medium and Figure 5 shows a similar section of diaphragm, passage and valve chamber enclosed in an insulated chamber containing cooling fluid which is maintained at the desired temperature by means of a cooling coil in the medium.

In Figures 1, 2 and 3 carbon dioxide is fed through one way valves 2 into the single-acting piston pump 1 and double-acting piston pump 8 and expelled through valve 3. The condenser 4 consists of a vertical tube 5 either closed permanently or connected to a valve 9 and surrounded by a jacket 6 in which circulates the coolant from the refrigerating equipment (not shown). The condenser is connected to the top of the end Wall of the cylindrical pump body by a short curved tube '7.

In Figure 4 the diaphragm 10 is alternately distended and allowed to relax by pulsations in a gaseous or liquid medium contained in chamber 11 which is in communication with a source of such pulsations via inlet port 12. When the diaphragm is distended part of the liquid in chamber 13 and condenser 14, which is cooled by the circulating coolant in jacket 15 is ejected through the outlet ball valve 16. On relaxation of the diaphragm, liquid to be pumped is drawn into the condenser 14 through the inlet ball valve 17, where it mixes with the cooled liquid I in the condenser 14 and thus its temperature is rapidly lowered. Liquid contained in chamber 13, therefore, is liquid which has been ejected into condenser 14 but not through outlet valve 16 during the distention of the diaphragm, and thus cooled, and has then been withdrawn into chamber 13 as the diaphragm has relaxed. Since mixing of the liquid drawn through inlet valve 17 and the liquid in chamber 13 is incomplete the liquid in chamber 13 remains at a low temperature.

A similar cycle of events takes place in the apparatus shown in Figure 5 but the condenser 14 is cooled by cooling medium 18 contained in the insulated container 19 which medium is maintained at a suitably low temperature by means of cooling coil 20 through which is circulated refrigerant.

I claim:

1. Apparatus for pumping readily vaporizable liquids comprising a pump having a pump casing enclosing a pumping chamber, inlet and outlet valves controlling the admission of readily vaporizable liquid to the pumping chamber and its discharge therefrom, a movable member operable within the pumping chamber to exert pressure upon the liquid to be pumped, and a condenser consisting of a tube of reduced cross-section with respect to the pumping chamber in combination with an external jacket for coolant, the condenser being at all times in direct connection with the pumping chamber and forming an enclosed and indivisible volume therewith.

2. Apparatus according to claim 1, in which one end of the condenser is in connection with the pumping chamber and the other end of the condenser is in connection with the inlet and outlet valves of the pump.

References Cited in the file of this patent UNITED STATES PATENTS 862,867 Eggleston Aug. 6, 1907 21,001,353 Salnikofr May 14, 1935 r 2,631,437 Bruce et a1. Mar. 17, 1953 2,705,406 Morrison Apr. 5, 1955 FOREIGN PATENTS 495,795 Germany Apr. 12, 1930 

